Variably shaped beam EB writing system

ABSTRACT

A variably shaped beam EB writing system which draws a pattern, comprises a recognition module, an adjustment module, and a drawing module. The recognition module recognizes at least one of a first length unit to specify a pattern length and a first position unit to specify a position described to a pattern data. The adjustment module adjusts at least one of a second length unit to specify a pattern length which is drawn by the variably shaped beam EB writing system and a second position unit to specify a position thereof to a value of which at least one of the first length unit and the first position unit are divided by a natural number. The drawing module draws a predetermined pattern based on at least one of the second length unit and the second position unit adjusted by the adjustment module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.10/255,580, filed Sep. 27, 2002, now U.S. Pat. No. 6,774,380 and isbased upon and claims the benefit of priority from the prior JapanesePatent Application No. 2001-302639, filed Sep. 28, 2001. The contents ofthese applications are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variably shaped beam EB (electronbeam) writing system.

2. Description of the Related Art

A manufacturing method of an LSI is as follows. A pattern on the mask istransferred to the resist, developed, and etched on the wafer using anoptical stepper or a scanner to form the resist pattern. Thereafter, thepattern of one layer is manufactured on the wafer through varioussemiconductor processes. Next, the LSI is manufactured by repeating theabove-mentioned processes by using the mask having another pattern.

The method of manufacturing the mask used for such the manufacture ofthe LSI is performed by exposing, developing, and etching the resist onthe mask with the variably shaped beam EB writing system.

There is the system by which the resist spread on the wafer is exposeddirectly by charged beams such as electron beams and the ion beams oroptical beams by a variably shaped beam pattern writing system which arealso used for the manufacturing method of such a mask.

Such the variably shaped beam EB writing system inputs the pattern datato which information in the pattern to be drawn is described and drawsthe pattern to be drawn by using information on this pattern data.

In general, a predetermined unit is specified explicitly or implicitlyregarding to the length or the position, and a digital value based onthis unit is described in the pattern data.

For instance, if a unit is 1.25 nm, 500 nm is set as “400”. This unitoriginates in the design of the variably shaped beam pattern writingsystem, and, for instance, is an inherent value to system decided by thebalance of an electro-optical system and a DAC performance of an analogcircuit for the electron beam exposure device.

In general, the position unit and length at the design of the LSI is setindependently to the inherent length unit and the position unit of theabove-mentioned pattern writing system.

For instance, it is assumed that the pattern transfer to resist ispreformed by an optical stepper and the device is designed with 1.25 nmas a unit. When the reduction rate of a used optical stepper is ⅕, alength unit of the design pattern on the mask becomes 6.25 nm.

On the other hand, it is assumed that the unit of the control of thevariably shaped beam pattern writing system to write pattern on the maskis 1 nm. At this time, the unit of the pattern on the mask becomes 6.25nm, and this cannot be represented with the integral multiple of 1 nm,which is the control unit of the variably shaped beam writing system.That is, mismatch between the unit of the pattern and the unit of thedevice is caused and the following various problems are caused.

The case where a certain pattern becomes a unit and is arrangedrepeatedly in the LSI pattern will be considered as an example. Thepitch of this repetition becomes the integral multiple of 6.25 nm on themask, too.

For instance, when the pitch is 1237.5 nm (6.25 nm×198), this does notbecome the integral multiple of 1.00 nm which is the unit of the device.The error is caused at the position of the pattern which is drawnfinally when data is made by ignoring the fractional portion of 0.5.

For instance, the shift at the position to which it extends it will begenerated in 0.5 nm×100=50 nm in the 100th pattern when there are 100repetitions.

In avoiding this, there is a method of rearranging the structure of therepetition in data. In this case, there is a problem that the amount ofdata increases because the data structure of pattern which originallyexpressed by one array changes more complicated one (such as datastructure expressed by several arrays).

The problem of positioning error also appears in the other case, asfollows. The original LSI pattern is sometime shrunk in order to enhancethe LSI performance. Let say the unit of the design of an original LSIpattern is the integral multiple of that of the variably shaped beampattern drawing device (for instance, 4 nm on the mask). If the LSI isshrunk by 0.8, then the length unit after reduction becomes 3.2 nm, anddoes not become the integral multiple of unit 1 nm of the variablyshaped beam pattern drawing device, and the above-mentioned problemappears again.

That is, even when the original pattern is 4 nm unit, if the LSI whosepattern is 0.8 times thereof is made, the length unit after reductionbecomes 3.2 nm, and does not become the integral multiple of unit 1 nmof the variably shaped beam EB writing system, and the above-mentionedproblem appears again.

On the other hand, there is a device which performs the reduction of theabove-mentioned entire pattern inside the device according to thevariably shaped beam EB writing system. For instance, after the data ofthe pattern to be drawn is input to the variably shaped beam EB writingsystem, the reduced pattern data is created from the data by using thecomputer attached by the device.

However, the calculation time becomes long in a case of reduction rate0.8, and exceeds the drawing time by far, and the entire system fallsinto the state of waiting for the end of such a calculation. Thisremarkably degrades the use efficiency of the entire system.

In addition, this kind of problem is occurred in the development of thenew pattern writing system as described below.

For instance, conventionally after putting the device of length unit of10 nm to practical use, the accuracy of the device has been improved bymaking the unit a half, such that the unit of first generation's deviceis 5 nm and the next generation thereof is 2.5 nm.

However, in a new device, it is necessary to draw the pattern data inconventional (Unit 2.5 nm) on the other hand in many cases. Therefore,the necessity for drawing the data with the conventional 2.5 nm unit inaddition to the data with 1 nm unit in a new device is caused.Therefore, the above-mentioned problem appears.

Therefore, the mismatch of the unit of the variably shaped beam EBwriting system and the unit of the pattern data becomes large, and theabove-mentioned problem is caused.

To avoid this, there is a method of assuming the unit to be not 1.25 nmbut 1 nm in the next generation's device after the device with 2.5 nmunit. As a result, mismatch can be avoided about the pattern data with 1nm unit.

On the other hand, a new device should draw in conventional pattern data(2.5 nm unit) in many cases. That is, the necessity for drawing the datawith conventional 2.5 nm unit in addition to the data with 1 nm unit iscaused in a new device. Therefore, the above-mentioned problem appears.

Various problems as mentioned above have been caused, since the unit ofthe pattern data and the unit of the pattern writing system shift likethis.

Moreover, in a stage continuous movement type Gaussian beam methodraster scan device, there is an example of a similar function.

This is assumed that

(1) A standard beam size (fixed value) (of Gaussian beam) is assumed tobe an integer multiple (n times) and a big beam is formed, and

(2) It is assume the scanning speed of the beam to be 1/n at a standard(fixed) speed.

However, in a case of the EB system which uses the variably shaped beammethod, since the shape and the size of the (shot) beam for each shotchange, a fixed beam size does not exist unlike the case of the Gaussianbeam.

Moreover, the beam position does not change continuously, but changes atrandom in the vector scanning method. Therefore, a constant beamscanning speed does not exist unlike the raster scanning method.

In addition, since it is necessary to control the beam position on thewide plane in the vector scanning method, in many cases, it becomesnecessary to correct the deflection distortion with higher-order(including terms more than second order of x² etc. concerning theposition).

After such a correction is performed two-dimensionally, it is necessarythat the change in the unit system is consistent in some method.

In addition to this, in the variably shaped beam method, not only theadjustment of positioning but also that of the beam formation is needed.

As mentioned above, by extending the technology performed with the stagecontinuous movement type Gaussian beam method raster scan device, it isimpossible to achieve the function to change the length unit and theposition unit in the device of the variably shaped beam vector scanningmethod.

The items to be adjusted include many things to achieve such a unitchange function with the device of the variably shaped beam vectorscanning method, and it is difficult to suit other correction functionsof the pattern writing system without the contradiction.

Actually, the device equipped with such a function is not reported.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a variably shaped beamEB writing system without the problem of mismatch of the above-mentionedunit without necessitating the many processing of the computer anddegrading accuracy.

The variably shaped beam EB writing system, which irradiates an energybeam and draws a pattern based on a pattern data to which predeterminedpattern information is described, according to the first aspect of thepresent invention is characterized by comprising: a recognition moduleconfigured to recognize at least one of a first length unit to specify apattern length and a first position unit to specify a position describedto the pattern data; an adjustment module configured to adjust at leastone of a second length unit to specify a pattern length which is drawnby the variably shaped beam EB writing system and a second position unitto specify a position thereof to a value of which at least one of thefirst length unit and the first position unit are divided by a naturalnumber; and a drawing module configured to draw a predetermined patternbased on at least one of the second length unit and the second positionunit adjusted by the adjustment module, to achieve the above-mentionedobject.

The variably shaped beam EB writing system, which irradiates an energybeam and draws a pattern based on a pattern data to which predeterminedpattern information is described, according to the second aspect of thepresent invention is characterized by comprising: a first unitconfigured to memorize at least one of a length unit to specify apattern length and a position unit to specify a position described inthe pattern data; a second unit configured to process at least one of adata of the length and the position of the pattern data as at least oneof a normalized length data and a normalized position data independenton the length unit and the position unit; a third unit configured toconvert at least one of the normalized length data and the normalizedposition data into a physical amount of a length and a position of apattern drawn by the variably shaped beam EB writing system; and afourth unit having a same pattern as the pattern described to thepattern data and at least one of a different length unit and a differentposition unit, configured to obtain a condition which becomes a samephysical amount when performing a conversion into the pattern lengthdrawn by the variably shaped beam EB writing system and a physicalamount of a position, correct the conversion by the third unit based onthe condition, and perform drawing based on the obtained physicalamount.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a configuration diagram of the variably shaped beam EB writingsystem used in the present invention; and

FIG. 2 is a figure which shows rectangular and triangular shots, and aposition of the origin.

DETAILED DESCRIPTION OF THE INVENTION

(First Embodiment)

Hereinafter, a variably shaped beam EB writing system according to thepresent invention will be explained in detail referring to the drawings.

FIG. 1 is a schematic diagram showing an electron beam pattern writingsystem used for the embodiment of the present invention.

The electron beam pattern writing system shown in FIG. 1 comprises asample room 10, a target 11 (sample), a sample stage 12, anelectro-optical tube 20, an electron gun 21, various lens systems 22 ato 22 e, a blanking board 23, various deflections systems 24 to 26, andbeam formation aperture masks 27 a, 27 b, and 27 c.

The electron beam pattern writing system further comprises a samplestage driving circuit 31, a laser measuring system 32, a deflectioncontrol circuit 33, a blanking control circuit 34, a variably shapedbeam size control circuit 35, a row substitution circuit and drawingcontrol circuit 36, a control computer 37, a data conversion computer38, and a CAD system 39.

The electron beam pattern writing system adopts the stage continuousmovement method. That is, the figure pattern is drawn by moving thestage continuously and controlling the beam position by deflecting thebeam.

A belt-shaped area of several millimeters in width which is drawn by onecontinuous movement in the stage is called a frame. All of the targetfigure patterns are drawn by repeating the drawing by continuousmovement in such a direction (direction of X) in the vertical direction(direction of Y).

The position control of the beam is performed with the main deflector 25and the sub-deflector 26 while continuously moving. The sub-deflector 26controls a position of the beam by about an area of 60 μm square (whichis called a sub-field). The positioning of the sub-field is performedwith the main deflector 25, and the range where the main deflection canbe positioned decides the width of the frame (Or, in other word,height).

The movement and the control of the stage is performed by sending themovement instruction from the control computer 37 to the sample stagedriving circuit 31. The content of the instruction is two instructionsof stop position and the stage speeds when it moves there. The stopposition is shown by the laser coordinates.

In a case of drawing the frame, the instruction is first sent to thesample stage driving circuit 31, and the stage 12 is moved to the frameorigin. Thereafter, after the instruction of the preparation is sent tothe drawing circuit 36, the instruction of the frame end position andthe stage speed is sent to the sample stage driving circuit 31.

The control software advances to the operation preparation of thefollowing frame drawing after confirming the movement end of the stage12 and the operation end of the drawing circuit 36.

The electron beam emitted from the electron gun 21 is turned ON or OFFwith the blanking deflection circuit 23. The electron beam patternwriting system enables the dose to be changed by adjusting thisirradiation time according to the irradiation position. The beam whichpassed the blanking board 27 a is formed to a rectangular beam and atriangular beam by the deflector 24 for the beam formation, the aperturemask 27 b and 27 c for the beam formation. Moreover, a size of arectangular and a triangular size thereof is varied.

The formed beam is deflected and scanned on the target 11 with the maindeflector 25 and the sub-deflector 26, and the desire pattern is drawnon the target 11 by the beam scanning.

The acceleration voltage of the electron beam in the electron beampattern writing system is 50 kV. The maximal variably shaped beam whichcan be generated is rectangle of 2 μm in height and 2 μm in width andfour kinds of right isosceles triangles.

Though eight poles are often used as various deflectors to secureaccuracy in the device actually used, to explain here easily, it isassumed the deflector with four poles is used, the voltage input to thedeflector from the amplifier is set to Vx, −Vx, Vy, and −Vy, and theindependent parameters are two kinds of voltages of the voltage Vx toX-direction and the voltage Vy to y-direction.

In the embodiment, the length unit and the position unit of the variablyshaped beam EB writing system is variable effectively and matches to thelength unit and the position unit of the pattern described to thepattern data.

For instance, when the unit on the pattern data is 1.25 nm, by changingthe unit of the variably shaped beam EB writing system to 1.25 nm, theposition accuracy can be maintained without cancellation of significantdigits, and the structure of the repetition of the pattern need not bechanged.

The case of changing the pattern data to 0.8 times in the variablyshaped beam EB writing system can be processed by setting the unit inthe variably shaped beam EB writing system to 0.8 times.

By matching the unit in the variably shaped beam EB writing system tothe unit of the pattern data, the problem of such a mismatch can besolved.

Several method can be considered as a method of matching the unit in thedevice to the unit of the pattern data.

By changing the condition of the lens of the electro-optical system, itis also possible to change the sensitivity of the EOS and to effectivelychange the length unit. However, the degradation of the drawing accuracymight be caused when such an excitation condition of the lens isfrequently changed.

To avoid this accuracy degradation, it is necessary to leave the entiresystem until an optical condition becomes stable with long time.Therefore, whenever the length unit changes in the reticle drawing, achange in an optical condition, a device stop until stabilizing anoptical condition, and change in an optical condition and the adjustmentprocessing are performed repeatedly and the production efficiency of thedevice will be remarkably degraded.

In addition, as other method, there is a method of changing the gain ofthe amplifier which amplifies the output voltage of the DAC.

However, the amplifier is an analog circuit and it is impossible tochange the gain for each reticle in general. The problem on accuracyoccurs if it forces it. Only, the one near the exception is a mainamplifier in the pattern writing system of the raster scanning.

Since the voltage is gradually changed for the pattern writing system ofthe raster scanning, the amplifier which uses the integration circuitcan be configured. However, since the voltage changes at random for thevector scanning pattern writing system, it is impossible to configurethe amplifier with such an integration circuit.

In the present invention, the function to change the unit of a peculiarlength and position to the device can be provided without changing thelens excitation condition of the above-mentioned electro-optical system,without changing the operation of the amplifier of each reticle (or,pattern), that is, without degrading the accuracy of the device anddeteriorating the efficiency of the device.

This method will be explained in detail as follows.

First of all, the EB is set so that the user can describe the data ofthe length and position of the input data in the input data. (Or, theuser can input the length unit of input data to the EB system whendrawing a pattern.).

The EB system can know the length unit and the position unit which theEB should match by taking in the “Length unit and position unit of inputdata” when drawing the pattern.

Next, though the EB system carries out necessary digital data processingusing the information about the position and the length recorded in theinput data, the digital processing does not use the unit of length indata, that is, processing is performed using normalized length andposition.

Next, the device converts the obtained data by the digital processinginto an input data for analog circuit, and inputs it to various analogcircuits.

Here, this conversion is performed with a digital circuit, and the dataconversion operation can be changed in the writing system.

This will be explained by the following example of processing positiondata.

The digital circuit output data is assumed to be (x, y).

The input data to an analog circuit is assumed to be (X, Y).

The digital conversion circuit converts the input data into the data foran analog circuit by calculating, for instance, the following equations.X=a×x+b×y+c×x ² +d×x×y+ . . .Y=p×x+q×y+r×x ² +s×x×y+ . . .

Here, though a, b, c, . . . , p, q are constants during calculating,these values can be changed when starting or resetting the circuit.

By changing these values, it becomes possible to change the operation ofdata conversion.

In the second invention, by changing the conversion operation, thelength unit and the position unit of the device is matched to the lengthunit and the position unit of the input data (to the device).

An outline of the method how to change the conversion equation will beexplained in the following.

The following two method may be applied to obtain the conversionequation.

(Method 1) First of all, the optimal conversion equation (standardconversion equation) for standard unit (ex. 1 nm) is obtained beforehandby an adjustment of EOS (electro-optical system) etc.

At drawing, by using given length unit and position unit, the conversionequation at drawing will be calculated under the following condition.

(Condition) “when the same pattern is described in two input data inwhich length and position are different, values after data conversionbecomes the same.”

A detailed explanation for obtaining the conversion equation will bedescribed later.

(Method 2) Though the conversion equation at length unit of the patternis finally obtained by adjusting the optical deflection system, as aninitial condition of the adjustment, the conversion equation obtainedunder the condition of (1) at this time is used. Even if the length unitchanges, the output value (for instance, DAC value) becomes the sameaccording to the condition of (1). The amount of the deflection becomesthe same, and the drawing result becomes the same, too. Therefore, it isa condition to make the drawing result the same even in a casedescribing with a different unit. In (2), the equation obtained by (1)is assumed to be an initial condition, the optical system and thedeflection system are adjusted, and the conversion equation for thelength unit of the pattern data is obtained.

At this time, the conversion equation obtained by (1) is correct if thestandard conversion equation is completely correct. The adjustment isended instantaneously after adjustment of the optical system since it isconfirmed that the conversion equation of (1) is effectively correct.The adjustment will be also ended in a short time still, since the errorof the equation obtained by (1) is a little in a case that there is alittle error in the standard conversion equation.

The position unit and the length unit in the device can be adjusted tothe length unit of the pattern effectively according to such aprocessing method.

The above-mentioned “Condition that the value after conversion by thelength unit and the position unit is not changed by the change of thisconversion operation” according to the present invention is disclosed asfollows.

The conversion equation f(x, y) (or the coefficient from which theequation can be led) is assumed to be already obtained in the lengthunit and the position unit which is used as a standard beforehand. Whenthe length unit is multiplied by k based on this, the conversionfunction F(x, y):F(x, y)=f(kx, ky)  (1)can be obtained.

This corresponds to the above-mentioned condition (The value afterconversion by the length unit and the position unit is not changed).That is, f(x, y) is obtained beforehand, and this function F(x, y) canbe used when the length unit and the position unit become k timesthereof at drawing. It can be proven that this function F(x, y) becomesa conversion equation when the length is multiplied by k based on theabove-mentioned restriction condition as follows.

If the length unit becomes k times thereof, the values x and y of thedata become x/k and y/k.

If these are substituted to the equation (1), the equation becomes asfollows:F(x/k, y/k)=f((x/k)×k, (y/k)×k)=f(x, y).

That is, since the physical amount (for instance, DAC value) obtained asa conversion result becomes the same even if the length unit ismultiplied by k, the drawing result becomes the same.

The example in a case that the conversion function f(x, y) is apolynomial will be shown as a specific example.

The conversion function when the length unit and the position unit is astandard value (pnm) is assumed to be represented as:f(x, y)=a+bx+cy+dx ² + . . . +ux ^(n) ×y ^(m)  (2)and specific numerical values after adjustment are obtained as each ofthese coefficients.

If a ratio (q/p) is shown by k when the length unit of the pattern datais qnm, the above-mentioned function F(x, y) is described as follows:F(x, y)=a+bkx+cky+dk ² ×x ² + . . . +u×(k ^((n+m)))×x ^(n) ×y ^(m)  (3)Here, if the equation (3) is transformed toF=a′+b′×x+ . . . u′×x ^(n) ×y ^(m)+  (4)The conversion coefficient is obtained as follows.a′=ab′=b×ku′=u×(k ^((n+m)))  (5)Since this case is one example in the above-mentioned general rule, thephysical amount (for instance, DAC value) obtained as a conversionresult even if the length unit is multiplied by k becomes the same, andthe drawing result becomes the same.

In the system, for instance, the coefficient group a, b, c, . . . , uwhich is adjusted with the standard unit is stored in the device. Thecoefficient is changed by the equation (5) when the unit is multipliedby k, a new coefficient is used, and equation (4) may be used.

In the polynomial of an arbitrary order, the adjustment rule of thecoefficient is as follows.

When the coefficient is obtained by a certain length unit and positionunit (snm), the coefficient is shown as follows when the length unit andthe position unit are assumed to be multiplied by k (unit is k×snm)

(Coefficient of X0^(m)×Y0^(n) at multiplication by k)

(Coefficient of x0^(m)×y0^(n) in standard unit)×k^((n+m))

(Adjustment of Main Deflection Position)

First of all, the unit adjustment concerning the main deflectionposition will be explained.

This unit adjustment is performed with the conversion circuit which isin former stage of inside the main deflection control circuit 33 in FIG.1 to the laser coordinates (Hereafter, called as a “Coordinatesconversion circuit”).

The coordinates conversion circuit converts the coordinates value (x0,y0) (normalized digital value) of the position given from the upperlevel into the value (x, y) on the laser coordinates and, at the sametime, corrects the position error which depends on the position on themask.

The coefficient group COEFd2r_a0 to COEFd2r_r2 to perform conversionfrom a digital value to the laser coordinate system and correction andthe sub-field size (1x, 1y) (digital value which uses the length unit onthe data) are given from the control computer 37 to this circuit. Theinformation is stored and recorded on the buffer memory in the circuit.

At drawing, the information (_x0, _y0) of the main deflection positionfrom the upstream is given to the circuit. This information is thecoordinates value of a left lower corner of the sub-field and is adigital value using the length unit on the data.

The circuit obtains the center coordinates (x0, y) of a sub-field as(_x0+1x/2, _y0+1y/2).

Next, the circuit performs the following calculation by using theconversion coefficient group and converts the value of the sub-fieldcenter position from the normalized value into the value in the lasercoordinate system.X=COEFd2r _(—) a0+COEFd2r _(—) b1×x0+COEFd2r _(—) b2×y0+COEFd2r _(—)c0×x0²+COEFd2r _(—) c1×x0×y0+COEFd2r _(—) c3×y0²y=COEFd2r _(—) p0+COEFd2r _(—) q0×x0+COEFd2r _(—)q1×y0+COEFd2r×r0×x0²+COEFd2r _(—) r1×x0×y0+COEFd2r _(—) r2×y0²

Here, the coefficients COEFd2r_a0, . . . can be set from outside of thecircuit.

Specifically, the value set from the outside is stored in the register,and the circuit performs the above-mentioned calculation by using theregister value.

That is, the conversion equation can be controlled by replacing thesecoefficients in the system.

The coordinates value (x0, y0) given from the upstream to the circuit isa normalized value. The value changes according to the use unit (forinstance, 1.25 nm and 1.0 nm, etc.), too.

On the other hand, the value which is converted into the lasercoordinate system should not depend on the former use unit and become aconstant correct value.

This adjustment can be achieved by adjusting the values of conversioncoefficients COEFd2r. The example of adjusting the coefficient will beshown as follows.

The length unit and the position unit of the electron beam patternwriting system is assumed be adjusted as 1 nm, and the coefficient atthat time is assumed to be from COEFd2r_a0 to COEFFd2r_r2.

If the coefficient when the unit is assumed to be Unm is fromCOEFd2r_a0U to COEFd2r_r2U, the following relational equation isobtained according to the equation (5).COEFd2r _(—) a0U=COEFd2r _(—) a0COEFd2r _(—) p0U=COEFd2r _(—) p0COEFd2r _(—) b0U=COEFd2r _(—) b0×UCOEFd2r _(—) b1U=COEFd2r _(—) b1×UCOEFd2r _(—) q0U=COEFd2r _(—) p0×UCOEFd2r _(—) q1U=COEFd2r _(—) q1×UCOEFd2r _(—) c0U=COEFd2r _(—) c0×U×UCOEFd2r _(—) c1U=COEFd2r _(—) c1×U×UCOEFd2r _(—) c2U=COEFd2r _(—) c2×U×UCOEFd2r _(—) r0U=COEFd2r _(—) r0×U×UCOEFd2r _(—) r1U=COEFd2r _(—) r1×U×UCOEFd2r _(—) r2U=COEFd2r _(—) r2×U×U

The conversion equation where the correspondence can be taken by settingthese coefficients in the circuit can be used.

Above-mentioned conversion coefficient and COEFd2r_a0 etc. at the unitof 1 nm are obtained beforehand, and the result thereof may be stored inthe control computer.

At drawing, the result and the unit of the pattern data described indata for the electron beam device are read, and then the conversioncoefficient when the length unit of data is used, i.e., COEFd2r_a0U,etc. can be easily calculated by using both of them according to theabove equation.

As mentioned above, the control software may input and set these valuesto the conversion circuit after obtaining the conversion coefficient.

The circuit memorizes the received coefficient in an internal buffermemory, and converts the coordinates value into the value in the lasercoordinate system by using this coefficient whenever the coordinatesvalue is input from the upstream. As a result, the length unitadjustment will be automatically performed.

In the latter part of the main deflection control circuit 33, there is amain deflection distortion correction circuit. The main deflectiondistortion correction circuit is a digital circuit which calculates theinput values Vx and Vy to the main deflection DAC amplifier with themain deflection position, i.e., the digital value (x, y), which isintended to be set and the read value (x, y′) of the laser interferencemeter etc.

Since the input pattern data has values in the laser coordinate systemthough the correction of the distortion etc. caused by anelectro-optical system etc. is performed, the length unit of the patterndata for former device has been processed. Therefore, the unit systemadjustment mechanism is unnecessary and usually processing may beperformed here.

(Adjustment of Sub-Deflection Position)

Next, the unit adjustment concerning the sub-deflection position will beexplained.

The sub-deflection control circuit performs the control of thesub-deflection position in a main deflection, that is, the control ofthe position of the beam.

The electron beam pattern writing system shown in FIG. 1 can form fourkinds of triangular beams in addition to four corner type beam. It isnecessary to adjust the sub-deflection position (swing back deflection)depending on the beam shape corresponding to this.

Therefore, amount of the voltages VoffsetX and VoffsetY (shot shape) forswing back of each beam shape can be set in the sub-deflection controlcircuit 33. Since the amount is shown by the voltage, if the adjustmentselection is performed by the predetermined length unit (1 nm), thevalue can be used as it is even if the length unit is changed.

FIG. 2 shows the origin of the sub-deflection coordinates of each shot.The rectangular 101 has an origin 100 in the left lower corner. Thepositions of the origin of other triangles are different depending onthe shape thereof.

This position of the origin is adjusted not to change on the sample sideabout the adjustment of an electro-optical system even though the beamsize is changed in each shape.

The correction coefficient Sd_r2 from sd_a0 to correct anelectro-optical distortion etc. and the sub-field size can be set fromthe control computer in the sub-deflection control circuit 33 as well asthe main deflection control circuit 33. The sub-field size is a digitalvalue which uses the unit in the data given to the device.

The code C showing the shape of the shot and the value (_x0, _y0)(digital value using the unit on the data given to the device) to whichinformation at the sub-deflection position is normalized are given tothe sub-deflection control circuit 33 at drawing, and the origin is atthe left lower corner of the sub-field.

The sub-deflection control circuit 33 calculates the sub-field centercoordinates (x0, y0) by (_x0+1x/2, _y0+1y/2). The voltage is thereaftercalculated according to the next equation.Vx=+VoffsetX(shot shape C)+sd _(—) a0+sd _(—) b1×x0+sd _(—) b2×y0+sd_(—) c0×x0² +sd _(—) c1×x0×y0+sd _(—) c3×y0²Vy=+VoffsetX(shot shape C)+sd _(—) p0+sd _(—) q0×x0+sd _(—) q1×y0+sd_(—) r0×x0² +sd _(—) r1×x0×y0+sd _(—) r2×y0²

Here, +VoffsetX (shot shape C) etc. are the amounts of the swing backadjustment of the sub-deflection according to the above-mentioned shotshape.

The adjustment parameters (sd_a0 etc.) for optical distortions etc. areadjusted and decided by the unit (1 nm) of predetermined length.

The change method is the same as the change of the above-mentioned maindeflection correction coefficient though it is necessary to change thiscoefficient when the length unit is changed.

The coefficient (sd_a0 etc.) when the length unit becomes U can becalculated according to the coefficient in 1 nm of the standard as wellas at the time of the adjustment of the main deflection.

The control computer reads the unit recorded on the pattern data for theelectron beam pattern writing system, and calculates the correspondingcoefficient. The length unit concerning sub-deflection positioninformation is adjusted by setting it in the sub-deflection controlcircuit.

(Adjustment of Formation Deflection)

Next, the adjustment of the formation deflection will be explained.

It is possible to set the coefficient sh_a0(C) and sh_r2(C) for thedistortion adjustment of the optical system according to the shot shapein variably shaped beam size control circuit 35. Here, C is a symbolwhich shows the shot shape.

The variably shaped beam size control circuit 35 stores and memorizesthese coefficients on the buffer memory inside thereof. At drawing, thevoltage Vx and Vy applied to the formation deflection are calculatedbased on the code (C) and the shot size (x0, y0) given from the upstreamcircuit according to the next equation.Vx=+sp _(—) a0(C)+sp _(—) b1(C)×x0+sp _(—) b2(C)×y0+sp _(—) c0(C)×x0²+sp _(—) c1(C)×x0×y0+sp _(—) c3(C)×y0²Vy=+sp _(—) p0+sp _(—) q0×x0+sp _(—) q1×y0+sp _(—) r0×x0² +sp _(—)r1×x0×y0+sp _(—) r2×y0²

In these coefficients (sp_a0 etc.), the length unit and the positionunit is set as 1 nm beforehand, and the coefficients are decided bydrawing and automatic adjustment. The coefficient for the unit of otherlength and positions can be calculated based on the coefficient in 1 nmas well as the main deflection and the sub-deflection, etc. asmentioning above.

The control computer reads the length unit recorded in the data for theelectron beam pattern writing system, and decides the correspondingcoefficient and sets it to this circuit, as a result, the unitadjustment might be preformed to the circuit.

(Control of Stage Position)

Next, the control of the stage position will be explained.

Since the stage position is performed by controlling the sample stagedriving circuit 31 and the unit is expressed in the laser coordinatesystem, this conversion is performed as follows.x=x0+x1×cv×x2×cv

Here, (x, y) is a position of the stage expressed in the lasercoordinate system. (x0, y0) is an expression of left lower corner of thereticle with the laser unit system and depends on the reticle size. (x1,y1) is a value to express the chip origin on the mask (chip left lowercorner) by the pattern data unit to make the left lower corner of thereticle standard. (x2, y2) is a value where the frame position isexpressed by each pattern data based on the origin of chip. As for theframe position, a right center of the frame shows a drawing endposition, and a left center of the frame shows a drawing origin. The cvis a conversion coefficient from the unit of the pattern data to theunit of the laser.

The change of the unit is performed by changing the value of the cv asfollows.

First of all, the conversion coefficient for the unit which is used as astandard beforehand is obtained. To assume the easiest processing, theunit which is used as this standard may be the same as a standard unitin the distortion correction as mentioned above etc.

The cv as described in equation (5) when the unit of the pattern databecomes knm which is multiplied by k of original unit if a standard unitis assumed to be 1 nm, and this conversion coefficient is assumed to becv0,CV=cv0×kcan be calculated.

(Control)

In the above-mentioned device configuration, the entire control is asfollows.

First of all, the coefficient for the position correction on the mask,the distortion of main deflection correction coefficient, thesub-deflection correction coefficient, and the formation deflectioncorrection coefficient are obtained beforehand by a predetermined lengthunit and unit (1 nm) of the position. These are obtained byauto-adjustment of the optical system and by actually drawing andmeasuring the test pattern.

Next, the obtained result is stored in the predetermined disk of thepattern writing system in the form of the file.

When drawing the predetermined mask, the control software reads thelength unit described in the pattern data for the electron beam patternwriting system. Moreover, the deflection coefficient of variousstandards obtained beforehand of the unit of predetermined length isread from the disk.

Next, various correction coefficient groups corresponding to the unit ofthe pattern data are calculated from the read unit of the pattern dataand various standard correction coefficients. This result is set in thelaser coordinates conversion circuit, the sub-deflection control circuit33, and the formation deflection control circuit 35.

The sub-field size information is set in the laser coordinatesconversion circuit and the sub-deflection control circuit 33.

Next, after reading the data of the frame from the file of the electronbeam drawing data and transferring it to the pattern data buffer memory,the software sets coordinates at the starting position and thecoordinates at end position of the frame in the stage control circuit,and thereafter starts various control circuits and the graphicsprocessing circuits.

The drawing processing circuit performs processing of development of thecompressed data and the shot division, etc. This processing is performedby using the digital data described in the pattern data as it is. Thatis, it is processed as the normalized amount.

After such a processing is performed, the data is sent to the maindeflection control circuit 33 and the sub-deflection control circuit 33,etc. as follows.

The data of the sub-field position is sent to the conversion circuit ofthe laser coordinates in the main deflection control circuit 33, and theadjustment of the length unit and the position unit is performed likethe above-mentioned and is converted into the laser coordinates here.And, the distortion of the electro-optical system is corrected with theoptical distortion correction circuit in the main deflection controlcircuit 33, and is converted into the voltage value. This voltage valueis input to the main deflection amplifier, and is applied to the maindeflector.

The shot position information and the code of the shape of the shot aresent to the sub-deflection control circuit 33. And, the unit conversionis performed in the sub-deflection control circuit 33, and informationat the shot position is converted into the voltage value. The value isinput to the sub-deflection amplifier, and is applied to thesub-deflector.

The shot size information and the code of the shape of the shot are sentto the formation deflection control circuit 35. And, the unit conversionis performed in the formation deflection control circuit 35, and theshot size information is converted into the voltage value. The value isinput to the deflection of the formation of the value amplifier, and isapplied to the formation deflector.

The timing adjustment etc. between each circuit may be performed asusual. For instance, after ending the sub-field positioning, the maindeflection control circuit 33 sends an electric signal to thesub-deflection control circuit 33 and the formation deflection controlcircuit. As a result, after positioning a sub-field, the shot in asub-field can be irradiated. The device operates an electric circuit,moves the stage while irradiating the beam, and stops the movement ofthe stage when reaching the end of the stage set by the controlsoftware. The control software recognizes the end of the movement of thestage, recognizes interrupt (Or, change in a predetermined register ofthe stage control circuit) by the stage control circuit, and repeats theabove-mentioned procedure to draw the following frame thereafter.

It becomes possible to match the unit of the device on the pattern datain each pattern to be drawn by such processing. Therefore, if onepattern data is set in the reticle, the adjustment of the unit of eachreticle will be performed. If two or more pattern data are set in onereticle and the length units thereof are different, the length units ofeach pattern data will be adjusted in one reticle.

(Second Embodiment)

Next, the second embodiment of the present invention will be explained.

The reduction of the entire pattern is performed in the variably shapedbeam EB writing system in this embodiment.

According to the variably shaped beam EB writing system shown in FIG. 1,it becomes possible to perform the reduction of the entire pattern inthe device as follows, in addition, the long calculation processingbefore drawing is not needed, and the position accuracy is not degraded.

At drawing the pattern on the mask, the data of the chip arrangementinformation on the mask in addition to the chip data (hereinafter,abbreviated as “Layout data”) is input to the device.

The reduction rate of each chip can be changed if the reduction rate ofeach chip can be described in this layout data. A concrete method of thereduction of the chip and drawing is as follows. The procedure atdrawing in one chip (reduction rate: 0.7) in the mask here will beexplained.

First of all, the control software of the variably shaped beam EBwriting system reads the reduction rate of 0.7 for this each chip fromthe layout data, and stores it in the memory of the control computer 37.Moreover, the length unit of the corresponding chip is read from thefile of the pattern data of the chip and is stored similarly.

Next, when 1.5 nm is described as a position unit length of the patterndata, the control software decides the length unit in the device as 1.5nm×0.7=1.05 nm.

The desired pattern will be formed if the 1.05 nm is assumed to be thelength unit, and the processing thereafter is as well as theabove-mentioned first embodiment.

If the length unit described in the pattern data 1.2 nm and themagnification described in the layout data is 0.9 in other chips in thesame reticle, 1.2 nm×0.9=1.08 nm may used as the unit at drawing.

Thus, the magnification of each chip in the mask is changed. Inaddition, it is possible to draw while adjusting the length unit of eachchip in the device.

Moreover, the conversion coefficient (conversion equation) is obtainedon the computer, set directly in the circuit, and used to draw in thesecond embodiment. However, a more correct conversion coefficient can beobtained by setting the obtained conversion coefficient to be an initialvalue and adjusting the deflection system before drawing the reticle.The conversion coefficient obtained in this manner is set in the circuitand is used to draw.

Though the length unit of the pattern is not the integer multiple of astandard unit of the device (length unit and position unit when anelectro-optical system is adjusted), naturally, the present inventioncan be applied at the integer multiple.

The unit of the control of the device is matched to the length unit ofthe pattern in the above-mentioned second embodiment, but it is notlimited to this. For instance, when the length unit is 1 nm, and whenthe device is adjusted the length unit of the pattern data is 2.5 nm,the length unit of the pattern data is converted with 1.25 nm which ishalf thereof, and the length unit of the device may be matched to 1.25nm.

This example will be shown as follows.

When the data is stored in the buffer memory or before storage thereof,if the value described in the data is twice, the unit of data becomes1.25 nm which is half thereof. The desire pattern can be drawn if thecontrol unit of the device is matched to this 1.25 nm.

According to this method, the rounding error which occurs by the digitalprocessing of the shot division with the drawing control circuit etc.becomes (1.25/2) nm, and becomes small more than rounding error (2.5/2nm) when processing like 2.5 nm.

That is, drawing with higher accuracy to use the length unit (2.5 nm) ofthe pattern as it is can be achieved.

Since as an operation of which data of position and size is doubled, thebinary data is shifted stored in the computer only by one bit, it ispossible to achieve it at easily and high speed.

This processing may be performed with the computer when transferring itto the buffer memory or may be performed with hardware as follows. Forinstance, the data described in the pattern data may be sent to thebuffer memory, and the data may be sent by bit-shifting when the data issent from the buffer memory to the circuit of the subordinate position.

The bit shift can be easily achieved since it is performed by way ofonly the shift register. It is possible to perform high-speed processingwithout disarranging the pipeline operation of the hardware.

The above-mentioned operation does not limit to twice and can beexecuted with an arbitrary multiple. If it is an n power of two, theoperation can be achieved by shifting n bits. Moreover, the operationcan be achieved by adding a binary value which is shifted by one bit tothe former binary value in case of three times. Correspondingly, theunit of the device control may be the (½)^(n) times of the pattern dataunit in the former case, and ⅓ times of the pattern data unit in thelatter case.

The present invention is not limited to the example of using theelectron beam pattern writing system of the variably shaped in maskdrawing method as described above. When the resist on the wafer isexposed directly with the electron beam pattern writing system of thevariably shaped method may be applied.

When the data is converted into a physical amount or the control unit ofthe device (laser coordinates value or the DAC value), the length unitand the position unit are adjusted. However, it is unnecessary toperform the adjustment at the same time as the conversion and is alsopossible to perform the adjustment about before and after theconversion.

For instance, when the unit is the k times of the standard unit, thedata before conversion may be converted as (x′, y′)=(x/k, y/k), andconverted to the physical amount and the control unit of the device byusing the conversion function f(x, y) from the value of (x′, y′).

Moreover, though only the polynomial is discussed as a conversion type,it is not limited to this, and it is possible to apply to an arbitraryequation. It is shown that the Gauss distribution can be used as anexample. For instance, when the optical system can be adjusted asf(x, y)=c×exp[−{( x−x0)²+(y−y0)²}/σ²],and the reference unit is 1 nm, it is assumed that the constants c, x0,y0, σ is decided and the values of constants c′, x0′, y0′, σ′ areselected.

The conversion equation when the unit is multiplied by k may be sown asfollows.F(x, y)=c×exp[−{(kx−x0)²+(ky−y0)²}/σ²]c×exp−{(x−x0/k)²+(y−y0/k)²}/(σ/k)²

The values of c, x0, y0 and σ can be set from the outside for thecircuit. When the unit is multiplied by k, each value is calculated onthe computer by the following equation and the result thereof may be setto the circuit. Then, the circuit may be operated.c″=c′x0″=x0′/ky0″=y0′/kσ″=σ′/σk

For instance, the adjustment of an electro-optical system is performedso that the length unit and the position unit are set as 1 nm once aweek. At each mask drawing, the correction coefficient may be adjustedby using the result by synchronizing with the change for the unit asmentioned above.

Moreover, a minute adjustment concerning the deflection of the opticalsystem can be performed before drawing in each mask in addition to theadjustment once a week. The minute adjustment may be performed for allitems or only for a part of items, for instance, a minute adjustment ofthe correction coefficient of the formation deflection.

Though the control software calculates the coefficients of thepolynomial of the conversion equation and sets them to the circuit, thepresent invention is not limited to this method.

For instance, the processing such as performing this calculation, andsetting the value to the register can be achieved in the circuit. Anabove-mentioned example (adjustment of the main deflection position)will be explained. In this case, when the optical system and thedistortion correction are adjusted, the coefficients, i.e., COEFd2r_b0,etc. in the obtained standard unit are recorded in the hard drive.

When the software is activated or the reticle is drawn continuously, thecontrol software reads the coefficient at the start, and sets thecoefficient in the circuit.

For instance, at drawing, the change rate U of the scale for each chipin the reticle (unit of the pattern data/standard unit) is set in thecircuit.

The circuit comprises the DSP for instance, and the conversionprocessing etc. of the coefficient may be described in the microprogramwhich operates it. In the DSP processing, as well as the above-mentionedfirst embodiment, from the coefficient COEFd2r_b0 etc. in standard unitgiven beforehand and the change rate U of the scale, the coefficientsuch as COEFd2r_bU may be obtained by:COEFd2r _(—) a0U=COEFd2r _(—) a0COEFd2r _(—) p0U=COEFd2r _(—) p0COEFd2r _(—) b0U=COEFd2r _(—) b0×UCOEFd2r _(—) b1U=COEFd2r _(—) b1×U. . .and the calculation result may be set to the register of a partcalculating the conversion equation in the circuit.

Or, the coefficient is not calculated by the DSP, but the circuit whichcalculates the conversion equation is changed from the above-mentionedembodiment. The calculation may be preformed by the following equation.x=COEFd2r _(—) a0+COEFd2r _(—) b1×U×x0+COEFd2r _(—) b2×U×y0+COEFd2r _(—)c0×U2×x0²+COEFd2r _(—) c1×U2×x0×y0+COEFd2r _(—) c3×U2×y0²y=COEFd2r _(—) p0+COEFd2r _(—) q0×U×x0+COEFd2r _(—) q1×U×y0+COEFd2r _(—)r0×U2×x0²+COEFd2r _(—) r1×U2×x0×y0+COEFd2r _(—) r2×U2×y0²

Here, COEFd2r_a0 etc. are the coefficients in standard unit as well asthe above-mentioned case. U is the change rate of the unit (unit of thepattern data/standard unit).

The above-mentioned unit adjustment may be performed for each reticle,or may be performed for every block in the reticle.

Here, the adjustment of the pattern data and the restriction of thedevice will be explained. Though only the sub-deflection position isdescribed for easiness, it is similar to the main deflection positionand the formation deflection.

It is assumed that the number of bits which can be input to the deviceto which the invention is applied is 16 bits (which is decided by thenumber of bits and the maximum swing width of the digital circuit (whichnormalizes the sub-deflection position). It is assumed that the maximumswing width of the sub-deflection is 64 μm (sub-field size: 64 μm), andthe standard conversion equation is obtained in 1 nm unit.

FIRST EXAMPLE

The input data is assumed to be the data of the conventional device andto be created that the length unit is 2.5 nm, the number of bits is 16,and the sub-deflection in the maximum swing width is 160 μm (sub-fieldsize is 160 μm).

At this time, it is impossible to correspond to sub-field size 160 μm onthe device. However, this problem can be corresponded easily bypreprocessing drawing.

For instance, the sub-field size of the data to be drawn may beconverted into 60 μm with the software at outside the device or on thecomputer attached to the device. Since the sub-field of 160 μm×160 μm isonly divided into 9 fields in the operation, the processing can befinished in a short time even if the software is used.

If the method explained in the above-mentioned embodiment is applied toadjust the unit of the device with 2.5 nm to the data to which theadjustment of the sub-field size is finished by the preprocessing asmentioned above, it is possible to draw the desired pattern.

SECOND EXAMPLE

It is assumed that the input data is the data of other devices (nextgeneration's device), and is created such that the length unit is 0.625nm, the number of bits is 17, and the sub-deflection in the maximumswing width is 100 μm (sub-field size 160 μm).

At this time, there are two following problems of (1) the sub-field sizeof data is larger than the sub-field size of 64 μm which can becorresponded by the device, and (2) the number of bits of the data islarger than that of bits of 16 which can be corresponded by the device.

However, these problems can be corresponded easily by the preprocessingdrawing. The sub-field size of the data to be drawn may be convertedinto 50 μm by the software at outside the device or on the computerattached to the device.

The sub-field size becomes 64 μm or less and the number of bits becomes16 bits, too by this operation. Since the sub-field of 160 μm×160 μm isdivided into 9 fields and number of output bits are changed in theprocessing, the processing can be finished in a short time even if thesoftware is used.

If the method explained in the above-mentioned embodiment is applied toadjust the unit of the device with 0.625 nm to the data to which theadjustment of the sub-field size is finished by the preprocessing asmentioned above, it is possible to draw the desired pattern.

Though, in the above-mentioned embodiments, though the example of thestage continuous movement method is explained, it is not limited to thisand it is possible to apply also the pattern writing system of the step& repetition method and the pattern writing system with the variablespeed stage.

By matching an effective control unit in the device, on the patternlength and the position unit, it become possible to control the increaseof the calculation time and the increase of the amount of data in theconventional art and draw the pattern on an accurate position. As aresult, it become possible to enhance the use efficiency of the variablyshaped beam EB writing system without degrading accuracy, and lower themanufacturing cost of the mask and the LSI.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the present invention in its broaderaspects is not limited to the specific details, representative devices,and illustrated examples shown and described herein. Accordingly,various modifications may be made without departing from the spirit orscope of the general inventive concept as defined by the appended claimsand their equivalents.

1. A variably shaped beam EB writing system which irradiates an energybeam and draws a pattern based on pattern data that includespredetermined pattern information, comprising: a recognition unitconfigured to recognize at least one of a first length unit defining apattern length and a first position unit defining a pattern position,both the first length unit and the first position unit being included inthe pattern data; a change unit configured to change at least one of asecond length unit and a second position unit of the variably shapedbeam EB writing system to a value of which at least one of the firstlength unit and the first position unit is divided by a first number,wherein the first number is a natural number; and a drawing unitconfigured to draw the pattern based on at least one of the changedsecond length unit and the changed second position unit.
 2. The variablyshaped beam EB writing system according to claim 1, further comprising:a memory unit configured to store a deflection amount of the energy beamor a position correction equation corresponding to the at least one ofthe first length unit and the first position unit, wherein the changeunit is configured to change the at least one of the second length unitand the second position unit based on the memorized position correctionequation or the memorized deflection amount.
 3. The variably shaped beamEB writing system according to claim 1, wherein the first number furthercomprises said natural number multiplied by a fraction.